1. Field of the Invention
The present invention relates to an adhesive sheet for processing semiconductor substrates, and more particularly to an adhesive sheet for processing semiconductor substrates comprising a base film and an adhesive layer containing specific ingredients.
2. Background Information
An adhesive sheet for processing semiconductor wafers and/or substrates are conventionally used to secure semiconductor wafers and/or substrates when the semiconductor wafers and/or substrates are diced and expanded, and the semiconductor wafers and/or substrates are then picked up and simultaneously mounted.
In this type of sheet, a UV- and/or radiation-transmittable base film is coated with an adhesive layer that undergoes a polymerization curing reaction by means of UV rays and/or radiation, and the adhesive layer is irradiated with UV rays and/or radiation after the dicing process, causing the adhesive layer to undergo a polymerization curing reaction, whereby the adhesive strength is reduced, allowing the individual pieces such as the semiconductor wafers, chips, or substrates to be picked up.
An adhesive sheet for semiconductor wafer processing has been proposed as this type of sheet, for example, the adhesive layer comprises a base polymer, a multifunctional urethane acrylate having a molecular weight of 15,000 to 50,000, a polyester plasticizer, and a photopolymerization initiator, where the photopolymerization initiator is included in a proportion of 1 to 50 weight parts per 100 weight parts base polymer (see Japanese Laid-Open Patent Application H06-49420, for example). The use of multifunctional urethane acrylate oligomers having a molecular weight of about 3,000 to 10,000 for the adhesive layer has also been proposed (see Japanese Laid-Open Patent Application S62-153376, for example).
Recent trends in environmentally concerned commercialization, however, have led to the adoption of halogen-free flame retardants and the use of stabilizers based on different types of metal soaps than in the past as additives, and to the use of resins, in conjunction with the above, that are different in terms of type, composition, and the like than those used thus far, to maintain the properties of the sealing resin.
Additionally, the individual pieces sometimes cannot be picked up in the pick up process if the adhesive strength of the adhesive layer has not been lowered to the desired level after UV irradiation in cases where the sealing resin and/or additives are not suitable for the adherends or the amount of the release agent (such as wax) that is generally applied to the sealing resin surface is insufficient or irregular, or the like. Forcibly picking up the pieces may result in separation in the interior of the sealing resin or a sticky residue over the entire surface of the sealing resin.